Hvac control panel for clearing fault code memory

ABSTRACT

A control panel for an HVAC unit is disclosed. The control panel includes a memory device storing a predetermined reset code that corresponds to a plurality of control signals and which memory device is configured to store a plurality of fault codes resulting from faults occurring during operation of the HVAC unit. The control panel also includes a plurality of terminals capable of receiving control signals from a source external the control panel and a processing unit configured to compare control signals received from the plurality of terminals to the predetermined reset code and further configured to erase the stored fault codes in the memory device in response to a determination that the received control signals match the predetermined reset code.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. Utility applicationSer. No. 11/051,651, filed on Feb. 4, 2005, allowed, entitled “Method ofClearing an HVAC Control Fault Code Memory”, the disclosure of which isincorporated as if fully rewritten herein.

FIELD OF THE INVENTION

The present invention is directed to a method of clearing an HVACcontrol fault code memory and more particularly to an automated methodof clearing an HVAC control fault code memory using a predetermined setof control signals.

BACKGROUND OF THE INVENTION

Integrated or combined controls or control systems are common in theheating, ventilating and air conditioning (HVAC) industry. It is commonfor these types of controls to have some type of limited diagnosticcapabilities, which typically result as an error code being translatedas a blink code on an LED (light emitting diode), or as a display on aseven segment display. Until recently, most of these error codes wereonly shown while the actual error was happening, or while a lock-outcondition persisted, while some controls might continue to display thefault code for a period of time after the fault condition abated. In anyevent, a loss of power to the control board resulted in a reset of thecontrols and the loss of any error information without the possibilityof recall. So, when a repair technician went to evaluate a problem,because the home or business owner had usually already shut power downto the unit, the error code was no longer displayed. The servicetechnician, upon arrival to the site, may also remove a metal panelwhich is often connected to a power disconnect switch. If this is donebefore looking through a site-glass for any applicable error codes (if asite-glass is even provided on the access door), again the potentiallyvaluable information of the error code would be lost. Unless the errorduplicates itself immediately upon test by the service technician, alengthy trial and error period may be required to finally find and thenfix the problem.

Over the last couple of years, an electrically erasable programmableread-only memory (EEPROM) and/or other non-volatile memory within acontrol panel has been used to store these error codes, such that theyare displayable even after a power loss and control reset, or areotherwise recallable, such as through the use of an error recallmechanism. In some cases, even multiple errors are recorded in theEEPROM or other non-volatile memory, such that a history of faults canbe saved and recalled. This type of error code information is extremelyvaluable to service technicians. Instead of an on-site servicetechnician waiting for a problem to re-occur, or trouble shooting abroken furnace, for example, through a long process of trial and errortechniques without any past history, the furnace control can direct thetechnician in the direction of the actual cause, and at least minimizethe amount of trouble shooting required. The fault codes that are storedin memory can typically be cleared using a communications command or aswitch such as a pushbutton on the control.

During production, HVAC units are typically tested after beingassembled. During this process, commonly called “run testing,” certainfaults may occur or may be introduced into the unit to test variousfunctions of the unit. These faults are stored in a fault code memory ofthe control. Prior to releasing the product for shipment to a customer,these faults must be cleared from the control memory so that the faultcode history begins with installation of the unit.

Prior art controls typically have a switch, usually a button, on thecontrol to clear the fault code memory, requiring that a factory workerinteract with the control to clear the memory. The button is typicallyprovided for a technician to recall errors stored in the fault codememory, but when held in a depressed fashion for a period of time, alsoacts to reset the fault code memory. Thus, a run test operator wouldtypically have to depress the button for a certain period of time toclear the fault code memory after testing. This time is usuallyrelatively long (several seconds) to make sure that the servicetechnician doesn't inadvertently clear the memory while displayingactive fault codes using the button. Pressing and releasing a controlswitch over and over may pose ergonomic problems for the worker andcreates the possibility of damage to the control by mishandling.Furthermore, the human element creates the possibility of other errors,such as those that may arise from inconsistent manipulation of thecontrol switch and the like.

Other types of prior art controls have a communications feature thatclear the fault code memory when the HVAC control receives a certaincommand via a communications port. While this technique overcomes somedeficiencies by eliminating the human element, the use of acommunications port requires that the run test station have the abilityto communicate with the communications control port. It also requiresthat a dedicated communications connection be made with the HVAC controlin addition to the typical thermostat signal inputs used for runtesting. This equipment is expensive and generally atypical in HVAC unittesting environments. Furthermore, making the communications connectionto the control requires additional time, which slows production.

Accordingly, what is needed is a method for clearing an HVAC controlfault code memory that overcomes these and other problems found in priorart systems.

SUMMARY OF THE INVENTION

A method for clearing an HVAC control fault code memory is disclosedthat limits or avoids human intervention and makes use of connectionsand signals already used in the unit testing process.

According to an exemplary embodiment of the invention, a method forclearing an HVAC control fault code memory is disclosed. The methodcomprises assigning a predetermined reset code to an HVAC controlsystem, the predetermined reset code comprising a plurality of controlsignals receivable by the HVAC control system, detecting control signalsat the HVAC control system, determining whether the detected HVACcontrol signals match the predetermined reset code and clearing a faultcode memory of the HVAC control system in response to the controlsignals matching the predetermined reset code.

According to another exemplary embodiment of the invention, a method fortesting an HVAC unit is also disclosed. The method compriseselectrically connecting a test station to a control system for an HVACunit, receiving control signals from the test station at the HVACcontrol system, comparing the received control signals to apredetermined reset code, operating the HVAC unit using the controlsignals received from the test station in response to the receivedcontrol signals being different from the predetermined reset code,detecting a fault condition during operation of the HVAC unit, storing acorresponding fault code in a fault code memory in response to detectinga fault condition; and clearing the fault code memory in response tocontrol signals received from the test station matching thepredetermined reset code.

According to yet another embodiment of the invention, a system foroperating an HVAC unit is disclosed. The system comprises an HVAC unithaving a control panel and a means for providing a plurality of controlsignals to the control panel. The control panel comprises a memorydevice to store a predetermined reset code, a fault code memory to storefault codes from faults occurring during operation of the HVAC unit,means for detecting the plurality of control signals received from themeans for providing a plurality of control signals, means for comparingthe detected plurality of control signals to the predetermined resetcode, means for operating the HVAC unit in response to the detectedplurality of control signals differing from the predetermined resetcode, and means for clearing the fault code memory in response to thedetected plurality of control signals matching the predetermined resetcode.

An advantage of the present invention is that it avoids the use of amanual onboard switch to clear the fault code memory and decreases oreliminates human intervention in the fault code clearing process.

Another advantage of the present invention is that it may increaseproduction process speed by incorporating logic into the HVAC controlthat reduces the time required to clear the fault code memory versus thetime required if using the onboard switch.

Still another advantage of the present invention is that it allows thefault code memory to be cleared after unit testing without requiringadditional communications equipment and it avoids the need to make anadditional connection for each unit built and tested.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart depicting a method for clearing an HVAC controlfault code memory according to an exemplary embodiment of the invention.

FIG. 2 is a flowchart depicting a method for clearing a furnace controlfault code memory according to an exemplary embodiment of the invention.

FIG. 3 is a flowchart depicting a method for clearing a heat pumpcontrol fault code memory according to an exemplary embodiment of theinvention.

FIG. 4 is a flowchart depicting a method for testing an HVAC unit havingan HVAC control with a fault code memory according to an exemplaryembodiment of the invention.

FIG. 5 is a schematic of a system for operating an HVAC unit accordingto an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

HVAC units, like most products, are typically tested after manufactureand prior to installation. In most test situations, a control board orpanel of a control system of the HVAC unit is typically connected to atest station. The test station typically includes a power source and anumber of switches. The test station sends control signals thatreplicate the control signals that would be received by the HVAC controlor control system when the HVAC unit is installed as part of anoperating HVAC system. For example, a furnace has a control that, wheninstalled, is connected to a thermostat. The thermostat sends controlsignals during operation to instruct the furnace, for example, to turnon or off or to operate a fan. Likewise, the test station is wired tothe HVAC control board to provide the same control signals duringtesting operations. By “control signals” is meant any analog signal orcombination of analog signals sent to the HVAC control system to provideinstructions or other information for the operation of the HVAC unit.

During run testing, the HVAC unit may experience faults that arecorrected prior to distribution or installation. Alternatively, if theHVAC unit experiences no faults during testing, faults may beintentionally introduced in the unit, for example, to determine that theunit is capable of properly detecting faults.

Faults may be recorded in a fault code memory of the HVAC controlsystem. If a fault occurs after installation, a service technician canreview the fault code memory to recall an error history that may behelpful in diagnosing a malfunctioning HVAC system or unit. However,fault codes recorded in the fault code memory during the testingprocedure need to be cleared, reset or deleted following testing so thatthe fault history corresponds to actual installation of the HVAC unit.This may avoid, among other potential problems, an erroneous diagnosisduring maintenance of the HVAC unit based on the fault code memorydisplaying a fault code for a fault that actually occurred prior toinstallation, i.e. during run testing at the factory.

Referring to FIG. 1, a method for clearing the fault code memory isprovided according to an exemplary embodiment of the invention. Themethod begins at step 100 in which a predetermined reset code involvinga plurality of preselected control signals is assigned to an HVACcontrol system having a fault code memory. The HVAC control system canbe a control device for any corresponding HVAC unit including, but notlimited to, furnace controls for a furnace, heat pump controls for aheat pump, air handler controls for an air handler, and compressorcontrols for a compressor-bearing unit, such as an air conditioner orheat pump. The HVAC control's fault code memory can be any suitableelectronic storage device as are known in the art and is typically anEEPROM or other non-volatile memory. Preferably, the fault code memoryis capable of storing fault codes from multiple occurrences or types offaults in memory and more preferably is capable of storing at least fivefault codes in memory at any one time.

The predetermined reset code used to clear the fault code memory is anydesired combination or sequence or timed arrangement of HVAC controlsignals that, when received by the HVAC control system, clears the faultcode memory. The control signals that comprise the reset code cause acertain logic sequence to occur in the control that clears the faultcode memory. For example, the reset code may be a series of switches,signals or terminals that are energized or de-energized for a certainperiod of time. The reset code is preferably selected such that theparticular sequence and/or combination of control signals would not bereceived by the HVAC control under ordinary conditions. In this way, thecontrol signals during normal operation, or even upon the occurrence ofa fault within the HVAC unit, would not inadvertently clear the faultcode memory of the HVAC control. The reset code is programmed into thecontrol when the control system is built, the reset code beingprogrammed into a memory device of the control system.

At step 120, the HVAC control detects the presence of the controlsignals. During testing, the control signals ordinarily come as inputsignals from a test station wired to the HVAC control to cause the HVACunit to behave in a desired fashion to test various aspects of the HVACunit. The test station may be as simple as a power source, typically 24VAC, and a series of switches connected via wires and/or relays to inputterminals on the HVAC control. The switches or relays are typicallyactivated by a computer programmed to test the HVAC unit. Afterinstallation of the HVAC unit, the HVAC control input signals wouldusually come from a thermostat or other device that provides controlsignals to an HVAC system.

Logic within the HVAC control then determines at step 130 whether thedetected input control signals match the combination and/or sequence ofcontrol signals that comprise the predetermined reset code. Amicroprocessor or similar processing device within the control makes thelogical comparison to make this determination. It will be appreciatedthat the type of control signals used to clear the fault code memory arethe same control signals sent to the HVAC control to operate the HVACunit. It is the combination and/or sequence and/or time arrangement ofthe control signals assigned in step 100 that determines whether anormal operating command is being given to the HVAC control or whetherthe input signals match the predetermined reset code corresponding to acommand to clear the fault control memory.

If a match is not present at step 140, the HVAC control performswhatever function is associated with the control signals received andthe method returns to step 120 to await receipt of additional controlsignals. If there is a match, the fault code memory is cleared or resetand any fault codes stored in the memory are deleted at step 150.

After the fault code memory is cleared, an output signal is returnedthat conveys the fault code memory has been cleared at step 160. Theoutput signal may be any signal capable of being monitored to verify thefault code memory has been cleared. Typically, the HVAC control isequipped with an LED which can be directed to flash a certain number oftimes, such as three flashes in two seconds, for example, as a signalthe memory has been cleared. The LED flash may be monitored by an actualindividual or using a device such as an electronic eye capable ofdetecting the LED illumination. Alternatively, or in conjunction with avisible output signal, such as an LED, an electronic output signal canbe returned to the test station via an output terminal on the HVACcontrol. Another way of communicating the fault code memory has beencleared may include activating a component of the HVAC unit, such as ablower or fan, for example.

FIGS. 2 and 3 demonstrate specific examples of control signalcombination sequences that can be used as a reset code to reset the HVACcontrol fault code memory.

FIG. 2 demonstrates an exemplary reset sequence for a furnace controlfault code memory, the furnace having at least two input terminals,including a heat terminal designated “W” and a fan terminal designated“G.” The terminals are turned on or off in order to transmit the controlsignals needed to reset the fault code memory. At step 200, power isapplied to the furnace control. W and G are both off for one second,then both on for one second at steps 210 and 220 respectively. Next, atstep 230, W is off for one second while G is on for that same second.Then, W is on for one second and G is off that second at step 240.Finally, W and G are both off for 1 second at step 250. With respect tothis example, this series of HVAC control signals matches the reset codeand when received, the fault control memory is cleared and an LED on theHVAC control flashes at step 260, indicating the fault control memoryhas been cleared.

It will be appreciated that this exemplary sequence could be modifiedusing different terminals or different combinations and that similarsequences could be implemented in HVAC units other than a furnace. Aspreviously discussed, combinations and sequences used as thepredetermined reset code are preferred that would rarely, if ever, bereceived by an HVAC control during normal operation of an HVAC unit.This is exemplified by the sequence of FIG. 2 that involves thesuccession of switching the fan and heat terminals on or off relative toone another for discrete periods of time.

It will be further be appreciated that additional logic could beincorporated into the HVAC control system that requires the input signalcombination and/or sequence to occur within a particular period of time,i.e., a timed arrangement. For example, again with respect to FIG. 2,the five combinations of W and G switching could be required to occurwithin a certain period of time after power-up. By way of furtherexample, the five one-second furnace control input signals of FIG. 2could be required to be completed within seven seconds of powering thefurnace. The furnace could be powered down after testing, the furnacehaving a number of faults stored in the control's fault code memory. Thetest station then powers up the furnace and sends the requisite controlinput signals to the HVAC control. If the sequence is completed withinseven seconds, the logic of the HVAC control would determine that thesequence was a command to reset the fault code memory and clear itaccordingly.

The HVAC control system may have a “test” input terminal that can beactivated to provide a test mode for an HVAC unit, such as a heat pumpor air conditioner, for example. The test mode may allow unit testing toproceed more quickly by shortening or bypassing certain timings ordelays of the HVAC control that would be executed prior to otheroperations of the unit during normal operation. A typical example oftest input terminal usage is to bypass an anti-short cycle delay timer.Such timers are often used on HVAC controls for compressor-bearingunits. The timer prevents the compressor from being energized within acertain period of time of being de-energized, typically several minutes.The test input provides a way to bypass the period of delay duringtesting.

FIG. 3 illustrates a sequence of control signals used to reset thecontrol fault code memory of an HVAC unit with a heat pump controlhaving a cooling input terminal designated “Y2” and a “test” inputterminal. The test input terminal is connected to the test station toprovide a test mode for truncated testing operations of the HVAC unit.After testing is complete, but prior to disconnecting the test inputterminal, the Y2 input is energized at step 300. While the Y2 input isbeing energized, the test input signal is shorted at step 310. Accordingto this example, this series of heat pump control signals matches thepredetermined reset code and thus clears the control's fault code memoryof any faults that occurred during the testing. At step 320, an LED onthe HVAC control is flashed three times to provide a visual confirmationthat the fault code memory has been cleared. Additionally, while the LEDflashes, an output terminal designated X/L is continuously energized bythe control, returning an electronic confirmation to the test station.

Methods used to clear the HVAC control fault code memory can beimplemented in a method of testing HVAC units as shown with reference toFIG. 4. At step 400, an HVAC unit having an HVAC control is electricallyconnected to a test station. As discussed, the test station may be assimple as a power source and a series of wires and switches that can beenergized or de-energized to send a signal to a particular HVAC controlterminal.

At step 410, the HVAC unit is operated via control signals applied toHVAC control terminals by the test station in performing a test sequenceto evaluate various aspects of the HVAC unit, such as verifying gasvalve or blower operation of a furnace or a defrost operation of a heatpump, for example. As the test proceeds, faults are stored in the faultcode memory at step 420. Different fault types can correspond toparticular fault codes to assist in the diagnosis of an HVAC unitmalfunction. The faults may occur as a result of a malfunction in theHVAC unit during testing or the faults may be induced to verify thefault code memory properly stores fault codes and that the stored faultcodes are associated with the correct type of faults.

As long as the test sequence continues, the HVAC control continues toreceive control signals from the test station to simulate the operationof the HVAC unit. Once the test is completed at step 430, the HVACcontrol receives from the test station a set of signals that matches thepredetermined reset code stored in the HVAC control at step 440. Thereceipt of the predetermined reset code indicates that the test iscomplete and that a command is being given to clear the fault codememory, which occurs at step 450. The HVAC control generates an outputsignal that indicates that the fault code memory has been cleared atstep 460.

FIG. 5 shows an exemplary testing arrangement 500. An HVAC unit 510having an HVAC control 520 is connected to a test station 530 via wires540. At least some of the wires 540 from the test station 530 areconnected to one or more terminals 550 on the HVAC control 520. It willbe appreciated that not all of the terminals 550 need be connected toall of the wires 540 of the test station 530 or vice versa depending onthe particular functions being tested on the HVAC unit 510. It willfurther be appreciated that a test input 551 need not necessarily beconnected when the HVAC unit 510 is being tested, depending on thedesired type of testing.

The HVAC control 520 also includes a fault code memory 560. The faultcode memory 560 can be any kind of memory device for storing fault codesduring operation of the HVAC unit 510 but is preferably an EEPROMmemory. The HVAC control 520 further includes an output device, whichmay include an LED 570, that can be used to flash stored error codes toa technician for diagnosis of a malfunction in addition to flashing apattern to confirm the fault code memory has been cleared after testing.Alternatively, or in combination with the LED 570, the output mayinclude sending a signal to a fault monitor input 526 of the teststation 530 from an output terminal 552, here designated as the X/Lterminal, of the HVAC control 520.

The test station 530 includes wires 540 that connect to the HVAC control520 to create a circuit and a power source 522, typically 24 VAC, todeliver the control signals to the HVAC control terminals 550 to testthe HVAC unit 510 and later to clear the fault code memory 560 aftertesting. The control signals are typically sent by opening or closingone or more switches 524 within the test station 530 to complete acircuit. Based on the pre-programmed logic executed by a microprocessor565 of the HVAC control 520, the HVAC control 520 directs the HVAC unit510 to perform certain operations depending on the control input signalsreceived. When the HVAC control input signals received by the HVACcontrol 520 match the predetermined reset code, the control fault codememory 560 is cleared and a confirmation is returned, which may beeither or both of an electronic output monitored by the test station 530via the fault monitor input 526 or a visible or other type of signalthat can be monitored by a person, such as, by way of example only,flashing the LED 570 or activating a component of the HVAC unit 510 suchas activating a fan or blower (not shown) of the HVAC unit 510 for ashort period of time.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A control panel for an HVAC unit comprising: a memory device storinga predetermined reset code and configured to store a plurality of faultcodes resulting from faults occurring during operation of the HVAC unit,the predetermined reset code corresponding to a plurality of controlsignals; a plurality of terminals capable of receiving control signalsfrom a source external the control panel; and a processing unitconfigured to compare control signals received from the plurality ofterminals to the predetermined reset code and further configured toerase the stored fault codes in the memory device in response to adetermination that the received control signals match the predeterminedreset code.
 2. The control panel of claim 1, wherein the predeterminedreset code comprises a predetermined sequence of control signals.
 3. Thecontrol panel of claim 1, wherein the predetermined reset code comprisesa predetermined combination of control signals.
 4. The control panel ofclaim 1, wherein the predetermined reset code comprises a timedarrangement of control signals.
 5. The control panel of claim 1, whereinthe memory device is an electrically erasable programmable read-onlymemory.
 6. The control panel of claim 1, further comprising an LEDconfigured to illuminate in response to erasing the stored fault codesin the memory device.
 7. The control panel of claim 1, wherein theplurality of control signals includes heating control signals, coolingcontrol signals, ventilation control signals, or combinations thereof.8. The control panel of claim 1, wherein the plurality of controlsignals correspond to control signals from a thermostat.